A power conversion device is mounted in an electric railway vehicle, converts power acquired from an overhead line, and supplies the converted power to an electric motor. The power conversion device, in response to, for example, an output voltage or an output current, performs operations such as control or protective stoppage of the power conversion unit. The power conversion device disclosed in Patent Literature 1 calculates a generated torque of an AC motor on the basis of two-axis current components calculated from an instantaneous current of an inverter output. This power conversion device detects a pulse component associated with a rectification current of the converter that is included in the generated torque, and adjusts a frequency of the AC output of the inverter on the basis of the pulse component.